Can a "correct" diet make you smarter?

The report below would seem to say so.  A small group of Finnish children who ate a traditional Finnish diet that was low on red meat, fat and sugar had better reading skills in third grade than did other kids in their classes.  And the study was a careful one with obvious confounding factors like social class ruled out.  What is to quarrel with there?

A lot.  Correlation is not causation and not all possible confounding factors were ruled out.  As is commonly the case, the researchers did not ask WHY some kids got a traditional diet while others did not.

An obvious possibility is that the parents who took the trouble to feed their children a traditionally "correct" diet were health conscious generally and that all we are seeing is the outcome of greater health consciousness.  Finland is a modern country so it  would undoubtedly have been easiest to feed kids Western convenience foods -- with their high levels of fat and sugar.  So the parents who did not do that stood out and may have had other different practices relevant to health -- avoidance of psychoactive drugs, for instance.

Poor health is indeed associated with damage to IQ so the dimmer students may simply have been less well-cared for generally.

Other points to ponder is that the sample was small, that the effects were statistically significant but small and that abilities at third grade are only weakly correlated with abilities in later life.  IQ rankings even in the teenage years can wash out in adulthood.

These observational studies are all well and good but there is no substitute for a controlled before-and-after study.  I include the journal abstract below.

Children who eat fruit, vegetables, fish, and whole grains in their first three years of school do far better in tests than their peers with poor diets, the study found.

The findings, from the University of Eastern Finland, were independent of children's socio-economic status, physical fitness, and body type.

It suggests healthy foods impact the brain in a way we do not fully appreciate, and could provide important evidence for public health policymakers globally.

The study involved 161 children aged between six and eight years old, and followed up on them from the first grade to the third grade in school.

The quality of their diet was analysed using food diaries, and their academic skills with the help of standardized tests.

The closer the diet followed the Baltic Sea Diet (high in vegetables, fruit and berries, fish, whole grain, and unsaturated fats and low in red meat, sugary products, and saturated fat) the healthier it was considered.

The study showed that children whose diet was rich in vegetables, fruit, whole grain, fish and unsaturated fats, and low in sugar, did the best in reading tests.

These healthy-eating children also showed the most progress in reading skills between grades one and three, compared to their peers with low-quality diets.

'Another significant observation is that the associations of diet quality with reading skills were also independent of many confounding factors, such as socio-economic status, physical activity, body adiposity, and physical fitness,' Dr Eero Haapala of the University of Eastern Finland said


Diet quality and academic achievement: a prospective study among primary school children

Eero A. Haapala et al.


Purpose:  Poor diet quality may impair academic achievement in children, but such evidence is limited. Therefore, we investigated the associations of healthy diet in Grade 1 assessed by Mediterranean Diet Score (MDS), Baltic Sea Diet Score (BSDS), and Finnish Children Healthy Eating Index (FCHEI) with academic achievement in Grades 1–3 in children.

Methods: The participants were 161 Finnish children who were 6–8 years old in Grade 1 and attended in a large ongoing physical activity and dietary intervention study. Dietary factors were assessed using 4-day food records, and MDS, BSDS, and FCHEI were calculated. Academic achievement was assessed by reading fluency, reading comprehension, and arithmetic skill tests. The data were analyzed using linear regression analysis and analysis of covariance adjusted for age, sex, parental education, household income, body fat percentage, physical activity, the PANIC Study group, and total energy intake.

Results: MDS was positively associated with reading comprehension in Grade 3 (standardized regression coefficient β = 0.167, P = 0.032). BSDS was positively associated with reading fluency in Grades 2–3 and reading comprehension in Grades 1–3 (β = 0.161–0.274, P < 0.05). FCHEI was positively related to reading fluency in Grades 1–2 and reading comprehension in Grades 1–3 (β = 0.190–0.344, P < 0.05). Children in the highest third of BSDS and FCHEI had better reading fluency and reading comprehension in Grades 1–3 than children in the lowest third (P < 0.05). None of the diet scores was associated with arithmetic skills.

Conclusions:  Healthier diet assessed by BSDS or FCHEI in Grade 1 was associated with better reading skills, but not with arithmetic skills, among children in Grades 1–3. Long-term intervention studies are needed to investigate the effects of improvements in diet quality on academic achievement among children.

Haapala, E.A., Eloranta, A., Venäläinen, T. et al. Eur J Nutr (2016). doi:10.1007/s00394-016-1270-5

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